Intro Game: Characters, Questions, and a Ritual of Fenicil

I'm a serial lurker, extremely occasional poster, just came here for some advice.

First of all, IT'S HAPPENING. I've finally got a group of people together to play this game. After years of having people say "Naw, I'm busy," or "I'm already playing Dungeons and Dragons," I've convinced five people to participate in an Ars Magica game potentially leading into a campaign.

The first issue to tackle is the fact that I'd rather not just jump straight into the saga; some amount of rules knowledge is appropriate before they can make wise decisions in character creation. So, the first game will be a scenario using pre-made characters. I'm going in with three goals: First, it should be fun. Second, they should have an idea of how the mechanics of Ars Magica work once it's done. Even with pre-made characters, it's difficult to teach the rules and have a story simultaneously. Third, I want it to tie in to the saga I'm planning on running, which will take place in the Transylvanian Tribunal and explore questions on the role of magi in society, and what the Order of Hermes should be doing. In order to try and work with some of these issues, I've concocted the following scenario:

A magus has been marched for a laundry list of Hermetic offenses, including interference with the mundanes, diabolism, impersonating a god, scrying on fellow magi, conspiring against the Order, and crossing the King's Road when the right of way belonged to the wagons. The list of charges is a bit trumped up, but that's not important. Five hoplites were sent to deliver the sentence of death, fighting their way into his mountain village home. Leading them on a chase through the regio containing his laboratory, captive spirits and many servants, the rogue wizard rebounded a spell upon one of them, leaving them dead, and managed to retreat to his sanctum. There, apparently cornered, he revealed his masterstroke: Lying in wait, a delayed ritual of Fenicil ready to unleash upon them! It was the very ritual used to break the hold of House Tremere, a mighty spell of confusion and madness. For better of worse the ritual botched, leaving everyone within the regio with gaping holes in their memories, unsure of who they are or why they were there. Due to the incomplete nature of the ritual, the memory loss is reversible through association, and will eventually fade over the course of a few days completely.

So, the characters start in the following situation. They awake, with no knowledge of who they are or what they want, in a strange town populated by similarly confused and angry people and pissed off spirits. Attempts to leave the village prove fruitless due to the nature of the regio, which none of them now know how to leave. There's a burnt dead corpse, the general feeling held by all that something frightening just happened, and a legal letter ordering the death of Aegidus of Guernicus for crimes against the order... now, if only they had a picture.

So, in short, it's a whodunnit Murder-Mystery in a closed village. As part of the memory-loss gimmick, I'll have cut the character sheets into pieces, and hand them back bit by bit as they figure things out about themselves. It'll start with just their belongings, appearance and personality traits, and flesh out from there. After they start a fight, a magus might get back a piece of paper titled "you seem to know how to handle yourself" with a list of combat-related skills.

I figure for Magi, Aegidus of Guernicus will be the strongest, with lots of Vim and a side of Theurgy and Spirit Magic. What would you suggest for the Hoplites? I figure I'll have a fire-slinging Flambeau and a some sort of spontaneous magic specialist in order to demonstrate two different uses of the magic system, but I'm not sure what to do with the other two.

Thoughts on the scenario? Thoughts on potential characters? Material I can cannibalize so I can have this ready by next Friday?

This is a fascinating idea! It sounds like a lot of work on your end, but if you can pull it off, seems like a lot of fun.
For the Hoplites, perhaps a couple different magical areas would work. Some of these could overlap.
Someone who specializes heavily in Perdo with a few forms like Corpus and Animal.
Someone who has very high combat scores and several Muto spells to buff up his defense and that of the group.
An Intelligo specialist (maybe this would work well for the Quaesitor)
A Mentem specialist, possibly also a Rego specialist for wards.

Another very good way to introduce people to the game is to first have them play grogs. This lets them dip a toe in without learning the entire magic system immediately.

I'm not convinced about this.

Playing a grog (or a companion) is (I think) a good way to introduce a single new player into a troupe of experienced players (at least some of whom are playing magi). As it lets the new player observe the magic system in action, without needing to know it. This is in fact, how I first played under 3rd Edition.

However, if no-one is playing magi, then it seems a bit pointless. You are not really introducing them to ArM unless there are player character magi.

So if I understand correctly; Aegidus, the marched magus, will be one of the amnesiac player characters. So, during the scenario, the player characters will realise that one of their number is in fact, the marched magus, and have to decide what to do about it. If so, that sounds like a great scenario to me.

For an introduction game, I think I would steer clear of things like Theurgy and Spirit Magic. I would just stick to plain vanilla Hermetic magic.

I would be inclined to make all the player characters, including Aegidus quite similar. Something like three Flambeau and three Guernicus (one of whom is Aegidus). By all means give them a few different formulaic spells each, but also give them a number of common spells. It will make it much easier to explain what to do if you only need to explain a few things. I don't think that you want to try to show everything that a magus can be. You can later explain to the players, that there are other Houses, and they will be able to see for themselves that there are other Art scores.

My personal thought would be to have Aegidus of Guernicus be the dead body, burnt by the flambeau on orders of the order, but who cast a massive PeMe spell before he died. Maybe with a moon duration, which he had figured would be enough time to slip away and get a good head start...
but work the campaign so it implies that one of the surviving magi is Aegidus.